I am a middle-aged immigrant Kiwi with professional background in engineering and a wide range of other interests. On this blog you will find essays on politics, society, science, technology, environment etc. Enjoy!

Climate change (2)

So, it is fair to say that in order to adhere to the AGW theory one must accept that:

The Earth is warming, largely as a result of human activity, with CO2 being the main culprit

The rate of this warming is unprecedented in recorded history and can lead to disastrous consequences

We, as humans, can stop or at least slow down the process

The issue is very complex but I have to start somewhere so let us first have a look at why we think the Earth is warming. We have kept temperature records for the last 150 years and they appear to show the general upward trend in mean air temperatures in most areas. In the old days keeping temperature records meant recording the readings of the good old mercury thermometers a few times a day. The chance of reading or writing down the wrong temperature was significant but these errors should be more or less random and not have a cooling or warming bias. As the technology advanced automatic weather stations were introduced and this is how the Earth temperature record is maintained these days. There are also the satellite records which started in 1979 but they come with their own set of reliability problems.

Which brings the issue of adjustments. There are many known (and probably also some unknown) biases in the recorded temperature readings. One major problem is the urban heat island (UHI) effect. As a result of land development weather stations tend to record higher temperatures over time because the surrounding new asphalt areas and roofs heat up more than say the grass they replace. Because grass keeps getting turned to asphalt but not the other way, this introduces the general warming bias to the readings. Many of the old weather stations were sited at the airports where the UHI trend is very pronounced. Airport runways keep getting extended but the warming this produces is purely local, not “global”. The temperature records are reportedly adjusted to remove the UHI warming bias but the accuracy of these adjustments is a matter of debate.

There is also a wider issue of the reliability of the historical temperature records. We are asked to believe that, for example, the records taken in China during the Great Leap Forward represent the actual thermometer reading. Millions of people were displaced during this period of social turmoil and millions died of famine. Yet, the weather station staff turned up everyday regular as clockwork to read the temperatures and record them accurately. Well, maybe they did but more likely they just made the numbers up while scraping for some food to fill their stomachs. To be fair, these readings may be wrong but should not be biased toward cooling or warming.

However, there are some cooling and warming biases which are all but impossible to correct. One hilarious example are the temperature readings from Siberia in 1950s through 1980s. I am sure my friend Nick who grew up there will appreciate this delightful story. Apparently, in a regulated Soviet economy, the coal for the municipal heating was allocated based on the recorded air temperatures. The colder it was, the more coal a city would get. So, the local officials would instruct the staff of the weather stations to record temperatures much lower than what they really were in order to get more coal for heating. These “official” records are now used to work out the global temperature trend which is biased toward warming (by the artificially lowered temperatures recorded in mid 1900s).

What I am saying here is that the global temperature records are nowhere near as reliable as we tend to assume. To say that the mean global temperature in year 1903 was say 13.64C is almost misleading. It may have been lower than now but to claim that we know to within 0.01C how much lower requires a leap of faith.